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Publication numberUS6239710 B1
Publication typeGrant
Application numberUS 09/445,878
PCT numberPCT/DE1998/000857
Publication dateMay 29, 2001
Filing dateMar 24, 1998
Priority dateSep 23, 1997
Fee statusPaid
Also published asCN1111829C, CN1261972A, DE19741853A1, EP1012805A1, EP1012805B1, WO1999016033A1
Publication number09445878, 445878, PCT/1998/857, PCT/DE/1998/000857, PCT/DE/1998/00857, PCT/DE/98/000857, PCT/DE/98/00857, PCT/DE1998/000857, PCT/DE1998/00857, PCT/DE1998000857, PCT/DE199800857, PCT/DE98/000857, PCT/DE98/00857, PCT/DE98000857, PCT/DE9800857, US 6239710 B1, US 6239710B1, US-B1-6239710, US6239710 B1, US6239710B1
InventorsUlrich Oppelt
Original AssigneeRobert Bosch Gmbh
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Smoke detector
US 6239710 B1
Abstract
A smoke alarm on the scattered radiation principle. Having a measuring field (5), accessible to smoke particles, in a measuring chamber, at which field the radiation direction of a radiation transmitter (6) is aimed, and scattered radiation occurring in the measuring field (5) can be received by a radiation receiver (7); the measuring chamber includes a portion of the hollow ellipsoid (3) which is mirror-coated on the inside; the measuring field (5) is disposed at the first focal point (1) of the hollow ellipsoid; the radiation receiver (7) is disposed at the second focal point (2) of the hollow ellipsoid (3).
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Claims(8)
What is claimed is:
1. A smoke alarm on the scattered radiation principle, having a measuring field (5), accessible to smoke particles, in a measuring chamber, at which field the radiation direction of a radiation transmitter (6) is aimed, and scattered radiation occurring in the measuring field (5) can be received by a radiation receiver (7), characterized in that
the measuring chamber includes a portion of the hollow ellipsoid (3), which is mirror-coated on the inside;
the measuring field (5) is disposed at the first focal point (1) of the hollow ellipsoid (3);
the radiation receiver (7) is disposed at the second focal point (2) of the hollow ellipsoid (3).
2. The smoke alarm of claim 1, characterized in that the hollow ellipsoid (3) is virtually completely closed and is provided with small openings (4) which however are large enough for smoke to enter.
3. The smoke alarm of claim 1, characterized in that one opening (4 a) for smoke entry into the measuring chamber is provided at each of the summits around the longitudinal axis of the hollow ellipsoid (3).
4. The smoke alarm of claim 1, characterized in that only a partial shell (9) of the hollow ellipsoid is used as a reflector, and the remaining opening serves to allow smoke to enter the measuring chamber.
5. The smoke alarm of claim 1, characterized in that a first radiation receiver (7 a) is provided for detecting the back scattering, and a second radiation receiver (7 b) is provided for detecting the forward scattering.
6. The smoke alarm of claim 1, characterized in that a light-emitting diode is provided as the radiation transmitter (6).
7. The smoke alarm of claim 1, characterized in that a semi-conductor laser is provided as the radiation transmitter (6).
8. The smoke alarm of claim 1, characterized in that a flash lamp is provided as the radiation transmitter (6).
Description
PRIOR ART

The invention is based on the generic type defined by the preamble to independent claim 1.

For detecting fires early, smoke alarms are generally used. One method of detecting smoke particles is to measure radiation scattered at smoke particles. Such smoke alarms based on the scattered radiation principle typically employ the method of forward scattering, because with it larger signals can be attained at the radiation receiver. Such a smoke alarm comprises a radiation transmitter (normally pulsed), a lens for focusing the rays, and a radiation receiver, for instance a photo diode, optionally with a lens for capturing the scattered radiation. Radiation receivers and radiation transmitters have no direct visual communication but instead are optically separated from one another by suitable mechanical provisions. There is an obtuse angle between the direction of radiation transmission and the direction of reception, and the scattering angle at the smoke particles to be detected is also obtuse.

Along with these forward scattering smoke alarms, there are versions with back scattering. In them, radiation transmitters and radiation receivers are disposed side by side, and the scattering angle is acute (German Patent DE 38 31 654 C2). A disadvantage of each of the known methods is that only a small proportion of the scattered radiation strikes the radiation receiver, while the remaining scattered radiation is lost to measurement. Also, only one of the preferred measurement effects is used at a time, that is, either forward scattering or back scattering.

ADVANTAGES OF THE INVENTION

The subject of the invention as defined by the characteristics of claim 1 has the following advantage:

The invention makes it possible to deliver virtually all the radiation scattered at the smoke particles to a radiation receiver in the form of a measurement signal. This signal includes not only the forward scatter and the back scatter but also the scattered radiation from all the ranges in between. This makes the measurement more sensitive overall, since there is almost no loss from uncaptured radiation. The smoke alarm of the invention also takes into account the scattering properties that are due to different particle diameters.

Advantageous refinements are defined by the dependent claims, whose characteristics can also be combined with one another as appropriate.

A light-emitting diode, semi-conductor laser or flash lamp can be provided as the radiation transmitter.

DRAWING

Exemplary embodiments of the invention are shown in the drawing and described in further detail in the ensuing description.

FIGS. 1 through 3 show schematic longitudinal sections through different smoke alarms according to the invention;

FIG. 4 shows a schematic prospective view of a further exemplary embodiment of the invention.

Elements that are substantially identical in different drawing FIGS. are identified by the same reference numerals.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows the basic arrangement in a section taken through the focal points 1 and 2 of a hollow ellipsoid 3. The hollow ellipsoid 3 is mirror-coated on the inside and is provided with openings 4, which are small in proportion to the inside surface area of the hollow ellipsoid 3, or in other words make up a maximum of 10% of the inside surface area, for example. The first focal point one and its immediate vicinity form the measuring field 5, where smoke particles can be simultaneously irradiated by a radiation transmitter 6 and detected by a radiation receiver 7 at the focal point 2. The radiation receiver 7 includes a radiation collector, which is mounted at the second focal point 2. However, it is also possible instead for the radiation receiver itself to be mounted there. As the radiation collector, it is possible for instance for one hemispherical lens each to be used for the half shell of the hollow ellipsoid 3 located below and above the plane of the drawing, respectively.

The radiation receiver may comprise one or more photo diodes or some equivalent component. The photo diodes can be disposed such that one preferentially receives the radiation from the back scatter and the other preferentially receives the radiation from the forward scatter, as suggested in FIG. 2, where the region of back scatter is indicated by the reception angle 8. This makes it possible for the scattered radiation, received from the various scatter angles, to be evaluated separately from one another in the same evaluation unit, and to draw conclusions from this about the kind of fire involved that is typical for the particle size found. Other suitable evaluations of angular ranges are also possible.

The mirror formed by the hollow ellipsoid 3 can, as shown in FIG. 1, be provided with a number of openings 4, which make it possible for the smoke particles to penetrate the measuring field 5. The openings 4 are small in terms of surface area occupied compared to the total surface area, so that there is no significant loss in terms of the portion of radiation reflected from the hollow ellipsoid 3.

As FIG. 3 shows, it is also possible for one or both summits to be cut open at the ends of the longitudinal axis of the hollow ellipsoid 3, to allow smoke to enter through an opening 4 a.

Finally, as shown in FIG. 4, it is possible to use only one partial shell 9 of a hollow ellipsoid, to allow free access to the smoke particles for measurement. This version is distinguished by a simple structure. It can be seen here that—as in the other drawings as well—a light trap 10 is disposed in the extension of the path from the radiation transmitter 6 to the measuring field 5. Retaining elements 11 for the radiation receiver 7 are shown schematically.

All the exemplary embodiments may, as is usual in optical smoke alarms, be provided with a labyrinth, to prevent extraneous light from entering the hollow ellipsoid 3.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4181439 *Mar 14, 1977Jan 1, 1980Cerberus AgSmoke detector with a conical ring-shaped radiation region
US4647786 *Oct 10, 1983Mar 3, 1987Cerberus AgPhotoelectric smoke detector and its application
US5127729 *Oct 15, 1986Jul 7, 1992Inotech AgMethod and apparatus for guiding and collecting light in photometry or the like
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7119899 *Jul 21, 2004Oct 10, 2006Lighthouse Worldwide Solutions, IncParticle sensor system
US7167099Oct 5, 2004Jan 23, 2007Gentex CorporationCompact particle sensor
US7502110Oct 9, 2006Mar 10, 2009Lighthouse Worldwide Solutions, IncDesign for particle sensor system
US7847700Jul 3, 2007Dec 7, 2010Conforti Fred JSystem and method for an optical particle detector
US7978087 *Nov 23, 2004Jul 12, 2011Robert Bosch GmbhFire detector
US8941505 *Oct 9, 2009Jan 27, 2015Hochiki CorporationSmoke detector
US9116121Oct 19, 2011Aug 25, 2015Uh Ventures LimitedSecond generation low-cost particle counter
US20050057366 *Oct 5, 2004Mar 17, 2005Kadwell Brian J.Compact particle sensor
US20060017926 *Jul 21, 2004Jan 26, 2006Pochy Rocco DImproved design for particle sensor system
US20070285661 *Oct 9, 2006Dec 13, 2007Saunders Thomas CDesign for Particle Sensor System
US20080258925 *Nov 23, 2004Oct 23, 2008Robert Bosch GmbhFire Detector
US20090009345 *Jul 3, 2007Jan 8, 2009Conforti Fred JSystem and method for an optical particle detector
US20110194111 *Oct 9, 2009Aug 11, 2011Hochiki CorporationSmoke detector
WO2014044967A1 *Sep 18, 2013Mar 27, 2014Efs SaDevice for measuring an amount of fluid injected by an injector
Classifications
U.S. Classification340/630, 340/628, 340/577, 340/578
International ClassificationG01N21/53, G08B17/107
Cooperative ClassificationG08B17/107
European ClassificationG08B17/107
Legal Events
DateCodeEventDescription
Dec 14, 1999ASAssignment
Nov 11, 2004FPAYFee payment
Year of fee payment: 4
Nov 20, 2008FPAYFee payment
Year of fee payment: 8
Nov 22, 2012FPAYFee payment
Year of fee payment: 12